A vital part of the production of cinema films is the “grading” process in which the exposure and colour balance of a “master” print are determined and agreed by the creative team. Subsequent processes, including distribution and final exhibition to an audience, should not change the appearance, or “look” that was decided upon at the conclusion of the grading process.
It is now becoming common for electronic methods of image storage and processing to be used in at least part of the film production process; and there is considerable interest in the use of electronics for distribution and for exhibition, using projectors where the image is generated electronically by a “light-valve” rather than from a transparent film medium.
For historical and other reasons relating to the development of television technology, the methods of working in television production and distribution are very different from those used for cinema film production and distribution. In particular, in television, it has been more usual for the “look” of the image to be decided at the time of acquisition in the camera, with only limited modification during the subsequent production processes. The technological limitations which led to this method of working are now becoming less stringent as a result of developments in electronic camera and image processing technology.
It is also now possible to use both electronic and photochemical processes at different stages in the production of the same film. The great flexibility offered by modern electronic image processing has potential benefits for film makers, but they need methods of working and systems which ensure that the electronic tools are used in a controlled and acceptable manner.
One area where electronic processing can help film makers is in simplifying the creation of “versions” of a film to be shown in different conditions and by different display technologies. Distribution processes can be defined which are guaranteed to have a small effect on the appearance of the images. It should then be possible to agree that in certain circumstances these processes can be used with less stringent requirements for review by the director.
FIG. 1 is a conceptual diagram of a film production and distribution process. A production process (1) feeds three distribution processes, each intended for a different display method. The film process (2) produces film prints for exhibition in cinemas; the electronic-cinema process (3) produces data for electronic projectors in cinemas; and the TV process (4) produces video data (usually on tape) which is distributed to TV sets.
The route through production (1) to film distribution (2) is well known, and will involve a grading process to determine an agreed exposure and colour balance, as indicated above, whose result will be checked by being projected in a reviewing cinema under controlled viewing conditions.
The inputs to the routes (3) and (4) could be obtained by scanning the graded film of route (2), or, possibly by taking information from earlier in the production process. There is no certainty that the end result will have the same “look” that was chosen in the reviewing cinema. This is so even if the graded film is scanned in a telecine since the process of colorimetric analysis in the telecine and presentation via an electronic display is almost certain to introduce errors.
The visual experience in the reviewing cinema will depend on the amount of stray light in that cinema and the way that light from bright parts of the image contaminates dark parts of the image (flare). Even in the cinemas at the end of the route (2), the viewing experience will probably be different from that in the reviewing cinema, because the level of stray light is unlikely to be the same (it is probably higher).